diff --git a/docs/操作系统/CS140e.md b/docs/操作系统/CS140e.md
deleted file mode 100644
index e69de29b..00000000
diff --git a/docs/系统安全/CS161.md b/docs/系统安全/CS161.md
index c7036515..04cd421d 100644
--- a/docs/系统安全/CS161.md
+++ b/docs/系统安全/CS161.md
@@ -24,7 +24,7 @@
 
 - 课程网站：<https://su20.cs161.org/>
 - 课程视频：参见课程网站
-- 课程教材：无
+- 课程教材：<https://textbook.cs161.org/>
 - 课程作业：7 个在线 HW + 3 个 Lab + 3 个 Project
 
 ## 资源汇总